Influence of experimental hyperglycemia on microvascular blood perfusion of pancreatic islet isografts.

The influence of hyperglycemia on the microvascular blood perfusion of pancreatic islet isografts of Syrian golden hamsters was analyzed by direct visualization of the islet's microvasculature by means of in vivo fluorescence microscopy. The experiments were performed using the hamster dorsal skinfold preparation, which allows for quantitative analysis of the microcirculation of islets grafted on the striated skin muscle. Islets were isolated from inbred hamsters by collagenase digestion and subsequently transplanted in normoglycemic (controls; n = 8) and hyperglycemic (65 mg/kg streptozotocin intravenously; n = 10) recipients. In both groups, revascularization of the islet grafts was completed on day 10 after transplantation. Quantitative analysis of capillary blood perfusion on days 6, 10, and 14 revealed no differences in functional capillary density and capillary red blood cell velocity of islets grafted into normoglycemic as compared to hyperglycemic animals. However, islet capillaries were significantly wider in hyperglycemic recipients (11.9 +/- 1.3 microns, P < 0.01) as compared to normoglycemic controls (8.9 +/- 0.4 microns). The increase of capillary diameters resulted in a significant rise (P < 0.01) of mean capillary blood perfusion from 1.76 +/- 0.39 nl/min in controls to 2.88 +/- 0.63 nl/min in hyperglycemic recipients, indicating an increase in microvascular blood perfusion due to hyperglycemia. From these results it is concluded that hyperglycemia is associated with higher capillary blood perfusion in revascularized islet isografts, similarly as known for pancreatic islets in situ.

Efficacy of myocardial initial reperfusion with 2,3 butanedione monoxime after cardioplegic arrest is time-dependent.

OBJECTIVE: In a previous study, initial reperfusion of isolated hearts after cardioplegic arrest with 2,3 butanedione monoxime (BDM) for 5 min was markedly superior to warm hyperkalemic reperfusion in improving the initial oxygen balance and reducing reperfusion arrhythmias. However, left ventricular contractility was only marginally enhanced. The goal of the present study was to test, wether the efficacy of BDM reperfusion can be enhanced by prolonging the application period. METHODS: 32 Langendorff perfused guinea pig hearts were subjected to 50 min of cardioplegic arrest in St. Thomas Hospital II solution at 37 degrees C for 50 min. Control hearts (n = 8) were immediately reperfused with normal Krebs solution for 30 min. In BDM-5, BDM-20, and BDM-40 hearts (n = 8, each), a 5, 20, or 40 min period of initial BDM reperfusion preceded perfusion with normal Krebs. RESULTS: BDM markedly improved the O2 balance during initial reperfusion by reducing O2 demand by over 50% (p < 0.01) in all treatment groups while coronary flow was maintained. Reperfusion contracture, estimated by the end-diastolic balloon pressure was inhibited by more than 50% in BDM-20 and BDM-40 hearts. Recovery of left ventricular developed pressure, dP/dtmax, and -dP/dtmax was significantly enhanced throughout the reperfusion period only in the BDM-20 group (p < 0.05). Myocardial ultrastructure was best preserved in BDM-20 hearts. CONCLUSIONS: 20 min of initial BDM reperfusion were clearly superior to immediate Krebs reperfusion or a shorter (5 min) or longer (40 min) BDM treatment period in attenuating reperfusion damage. Thus, contraction uncoupling during initial reperfusion by BDM or similarly acting drugs may prove a viable technique to reduce myocardial reperfusion damage in patients undergoing open heart surgery.

Prevention of initial perfusion failure during xenogeneic ex vivo liver perfusion by selectin inhibition.

BACKGROUND: Endothelial cell activation triggered by xenoreactive antibodies and complement products is the main feature of discordant xenograft rejection. The contribution of early cell-mediated mechanisms to this rejection process is poorly understood, and the function of adhesion molecules in xenogeneic cell interactions in vivo is unclear. The aim of the study was to investigate the role of selectins in mediating cell-dependent initial perfusion failure and functional restrictions in xenoperfused guinea pig (GP) livers. METHODS: Isolated GP livers were hemoperfused in a flow-constant, recirculating perfusion system via the portal vein. Microhemodynamic parameters such as sinusoidal perfusion rate and leukocyte flux were analyzed using intravital fluorescence microscopy. Hepatic oxygen consumption and bile production, as well as liver enzymes, potassium level, and numbers of white blood cells and platelets in the perfusate, were determined. The GP livers were perfused either with GP blood (control perfusion), with unmodified rat blood (xenoperfusion), or with rat blood treated with the selectin-blocking polysaccharide Fucoidin. RESULTS: A significant sinusoidal perfusion failure was observed in the xenoperfusion group, which was accompanied by distinct signs of a functional restriction-like reduced oxygen consumption, bile production, and increased perfusion pressure. However, there were significantly fewer impairments in the Fucoidin group. Furthermore, fewer platelets were trapped and a smaller number of stagnant leukocytes were observed in this group. CONCLUSION: Fucoidin did not suppress complement activation during xenoperfusion. Considering that Fucoidin inhibits the selectin-dependent interactions among white blood cells, platelets, and sulfate-containing proteoglycans on the surface of vascular endothelium, these findings suggest an important role for early cellular interactions in the development of organ failure during xenogeneic rejection.

The influence of organ temperature on hepatic ischemia-reperfusion injury: a systematic analysis.

BACKGROUND: Although hepatic ischemia-reperfusion (I/R) injury can be reduced by cooling of the ischemic organ, a systematic in vivo analysis of the influence of organ temperature in I/R injury is missing. The aim of this study was to systematically investigate the impact of defined temperatures of the ischemic liver tissue on microvascular I/R injury. METHODS: Ischemia of the left liver lobe was induced in C57BL/6 mice for 90 min. The ischemic lobe was placed in a polyethylene well and the temperature was adjusted to 37 degrees C, 26 degrees C, 15 degrees C, and 4 degrees C by superfusion with cooled/warmed saline solution. The ischemia groups (n=7 each) were compared with a sham-operated group (n=7). The sinusoidal perfusion index and the number of leukocytes firmly adherent to the endothelium of postsinusoidal venules were assessed using intravital fluorescence microscopy at 30 min, 120 min, and 240 min of reperfusion, respectively. At the end of the experiment, serum activities of the liver enzymes aspartate aminotransferase/alanine aminotransferase were determined, and tissue specimens were examined by electron microscopy. RESULTS: Core body temperature did not differ significantly between the groups. In the 37 degrees C group, the sinusoidal perfusion index was significantly reduced and the number of adherent leukocytes was significantly increased compared with the sham group. In all hypothermia groups, however, the microcirculatory parameters did not differ from the sham group. Serum activities of aspartate aminotransferase/alanine aminotransferase were significantly increased and hepatocellular integrity was severely affected in the 37 degrees C group as compared with all other groups. CONCLUSIONS: These findings demonstrate that in the mouse liver the known protective effect of hypothermia is already encountered at 26 degrees C. Further reduction of temperature did not generate additional protection from I/R injury.

Microcirculatory failure after rat liver transplantation is related to Kupffer cell-derived oxidant stress but not involved in early graft dysfunction.

BACKGROUND: Microcirculatory failure, activation of Kupffer cells (KC), and the formation of reactive oxygen species (ROS) are considered pivotal mechanisms of reperfusion injury after orthotopic liver transplantation. However, the sequence of these events and their impact on early graft function remain controversial. We therefore investigated whether KC induce microcirculatory disturbances through ROS release and whether microcirculatory failure contributes to early graft function after liver transplantation. METHODS: Donor livers of Lewis rats were pretreated either with saline or with gadolinium chloride (GdCl3), an inhibitor of KC function (n=8 each). Syngeneic OLT was performed after 24 hr of hypothermic preservation in University of Wisconsin solution. RESULTS: Intravital microscopy revealed significantly higher sinusoidal perfusion rates in GdCl3-treated allografts (92+/-1.1% vs. 75.7+/-0.8%; P<0.001) compared with untreated controls; permanent leukocyte sticking in sinusoids (23.5+/-2.1 vs. 62.6+/-3.3 cells/lobule, P<0.001) and in postsinusoidal venules (153.1+/-10.4 vs. 446.6+/-46.4 cells/mm(2), P<0.001) were markedly attenuated in GdCl3-treated allografts. Improvement of microcirculatory parameters in GdCl3-treated livers was correlated with a significant reduction of plasma glutathione disulfide formation by KC-derived ROS (0.96+/-0.1 microM vs. 1.79+/-0.5 microM; P<0.01). Despite these beneficial effects, GdCl3-pretreatment failed to improve postischemic alanine aminotransferase release and bile flow. CONCLUSIONS: Microcirculatory failure after liver transplantation is related to KC-derived oxidant stress but not involved in early graft dysfunction.

Impact of dextran on microvascular disturbances and tissue injury following ischemia/reperfusion in striated muscle.

The aim of this study was to evaluate the effect of dextran (Dx) 1 versus Dx 60 (molecular weights 1,000 and 60,000) on microvascular disturbances and tissue injury in striated muscle after ischemia/reperfusion (I/R). Experiments were performed using a 4 h pressure-induced ischemia model in the hamster dorsal skinfold chamber. Three groups (n=6) of animals received a continuous infusion (45 min, 3 microL/min) of either Dx 1 or Dx 60 (total dose 5 mg/kg) or saline solution beginning 15 min before reperfusion. Intravital fluorescence microscopy allowed for quantification of functional capillary density, leukocyte adherence, extravasation of fluorescein isothiocyanate-Dx, and nonviable (propidium-positive) cell count before ischemia and .5, 2, and 24 h after reperfusion. Experiments were terminated with tissue preservation for electron microscopy. Postischemic functional capillary density was significantly improved by Dx 60 (at 24 h, 88% vs. 51% in controls). In animals receiving postischemic Dx 1 or Dx 60, leukocyte adherence was significantly reduced (at .5 h, 44% and 58%, respectively) as compared with controls, whereas macromolecular extravasation was unchanged. Nonviable cell count was significantly decreased by both Dx fractions (at 24 h, Dx 1, 75%; Dx 60, 87%), indicating a reduction of tissue injury, which was also confirmed by electron microscopy. These results provide evidence that Dx 60 at 5 mg/kg attenuates I/R injury more effectively than Dx 1. Leukocytes play a major role in the development of I/R injury, but macromolecular extravasation does not always correlate with the leukocyte-endothelium interaction and the manifestation of I/R injury.

Liver ischemia and reperfusion induces a systemic inflammatory response through Kupffer cell activation.

To study the role of Kupffer cells (KC) as a cellular source of proinflammatory cytokines in hepatic ischemia/reperfusion, Sprague-Dawley rats were subjected to 20 min global hepatic ischemia. Sham-operated animals served as controls. Blood levels of tumor necrosis factor-alpha (TNF-alpha), interleukin-1 alpha (IL-1 alpha), and interleukin 6 (IL-6) were determined after 10, 30, 60, 120, and 240 min of reperfusion and compared with spontaneous cytokine release by KC isolated after 60 min of reperfusion. Hepatic ischemia/reperfusion resulted in an enhanced (p < .01) spontaneous release of TNF-alpha (+482%), IL-1 alpha (+33%), and IL-6 (+175%) by KC. Kinetic analysis of cytokinemia revealed an early increase (p < .01) of TNF-alpha and IL-1 alpha within minutes upon reperfusion, while an elevation of IL-6 serum levels was observed with a delay of 2 h. Early cytokinemia was associated with dysfunction/injury of the liver, lung, and kidney after 4 and 24 h of reperfusion, respectively. These data indicate that hepatic ischemia/reperfusion results in Kupffer cell activation and increased cytokine levels, which may produce systemic inflammation and may be responsible for tissue injury locally and on remote sites.

Modulation of kupffer cell activity by gadolinium chloride in endotoxemic rats.

Gadolinium chloride (GdCl3) has been reported to block Kupffer cell (KC) phagocytic activity in rats. In this study, we investigated the action of GdCl3 on Kupffer cells and related effects in response to lipopolysaccharide (LPS) exposure of rats. Using intravital fluorescence microscopy (IVFM), the hepatic microcirculation (phagocytic activity and zonal distribution of KC, sinusoidal perfusion, leukocyte-endothelial cell interaction) of rats pretreated with either saline or GdCl3 (10 mg/kg i.v. for 2 days) was studied at 1 h (n = 14) and 16 h (n = 16) after exposure to Escherichia coli LPS (10 mg/kg i.v.). LPS-exposure (1 h) resulted in KC activation with increased phagocytic activity (IVFM), intracellular enrichment of phagocytic vacuoles, and marked rise of cytokines (tumor necrosis factor-alpha, interleukin-6) in serum, whereas GdCl3-pretreatment completely inhibited the LPS-related KC response. 16 h after LPS-exposure, saline-treated animals revealed high serum levels of LPS, associated with microvascular perfusion deficits, marked KC destruction, and hepatocellular disintegration, which finally resulted in a mortality rate of 47% (7/15). In contrast, none of the GdCl3-treated animals died (0/8). GdCl3-pretreatment significantly attenuated LPS-induced hepatic microvascular perfusion failure and parenchymal cell injury at 16 h after LPS exposure. Intact KC morphology and low serum levels of LPS indicated adequate clearance capacity. Based on these results, we propose that modulation of LPS-induced KC phagocytic activity and KC function by GdCl3 is effective to protect from LPS-induced hepatic injury and systemic toxicity, probably by inhibition of overwhelming inflammatory response.

Endothelin (ET)-1 induced mucosal damage in the rat small intestine: role of ET(A) receptors.

The role of endothelin (ET)-1 as a mediator of small intestinal mucosal perfusion failure and tissue damage was investigated in the rat using intravital fluorescence videomicroscopy. The effects of intravenous infusion of ET-1 (3 nmol/kg) on functional capillary density, mucosal thickness, and the degree of mucosal damage were evaluated. Administration of ET-1 caused pronounced mucosal injury with a significant reduction of mucosal thickness compared with vehicle-treated control animals. Concomitantly, villous functional capillary density was markedly reduced 30 and 90 min after the infusion of ET-1. ET(A) receptor blockade by pretreatment with BQ 610 or with the novel ET(A) receptor antagonist ETR-P1/FL peptide prevented ET-1 induced capillary perfusion failure and mucosal damage. In contrast, the ET(B) receptor antagonist IRL 1038 was not effective. These results indicate that, acting via the ET(A) receptor, elevated levels of circulating ET-1 under various pathophysiological conditions, such as septic or hemorrhagic shock, might impair nutritive perfusion of the intestinal mucosa and contribute to tissue injury.

Use of selective and nonselective nitric oxide synthase inhibitors in rat endotoxemia: effects on hepatic morphology and function.

Endotoxin has profound effects on nitric oxide (NO) production, and considerable controversies exist as to whether these alterations are beneficial or deleterious. Increased mortality has been reported from nonselective inhibition of NO synthase. Results from selective inhibition of the inducible isoform (iNOS) appear largely positive. In a model of rat endotoxemia we have compared the early effects on hepatic morphology and function of selective and nonselective NO inhibition. Two hours after endotoxin injection (5 mg/kg intraportally) the rats were treated with either the selective iNOS inhibitor aminoethyl isothiourea (AE-ITU, 10 mg/kg), the nonselective NOS inhibitor NG-nitro-L-arginine methyl ester (L-NAME, 10 mg/kg), or normal saline. The animals were observed for another hour. Using an immunohistochemical method, induction of iNOS was demonstrated in various tissues in all slices examined. No unequivocal benefit from NO inhibition was noted. Electron microscopic examination revealed widespread alterations of liver morphology, without obvious differences between the groups. Liver function, as assessed by ketone body ratio, hepatic venous acid base values, and bile production, was generally more adversely affected after NO inhibition. Even with the iNOS selective inhibitor AE-ITU no benefit was noted. We conclude that during the early phases of endotoxemia therapeutic reduction of NO production has no positive effects on liver function or morphology.

Ischemia and reperfusion in pancreas.

Ischemic diseases of heart and brain are the primary causes of mortality in industrialized nations. The ischemic injury with the consecutive reperfusion is responsible for the disturbance of microcirculation with ensuing tissue damage and organ dysfunction. Recent evidence suggests that oxygen-derived free radicals and activated polymorphonuclear leukocytes produced in ischemic tissue are instrumental in the development of ischemic cell injury. In pancreas, ischemia/ reperfusion is proposed as a potentially damaging factor accounting in part for the pathogenesis of acute pancreatitis. Apart from ischemia/reperfusion injury, the kallikrein-kinin system mediates acute inflammation associated with enhanced capillary permeability and accumulation of polymorphonuclear leukocytes, cardinal features of ischemia/reperfusion injury also in acute pancreatitis. Therefore, it seems reasonable to use bradykinin-antagonists to influence postischemic reperfusion injury of the pancreas. In the following, we describe the pathophysiology of ischemia/reperfusion injury with special reference to the pancreatic microcirculation and morphological changes as observed in a model of complete and reversible ischemia. Furthermore, we will discuss the effects of two bradykinin-antagonists (HOE 140 and CP-0597) on functional integrity of the pancreas after ischemia/ reperfusion.

The nitric oxide donor sodium nitroprusside protects against hepatic microcirculatory dysfunction in early endotoxaemia.

OBJECTIVE: Endotoxin rapidly inhibits the activity of the constitutive endothelial nitric oxide synthase (ecNOS); this precedes the production of NO from inducible NOS (iNOS). This leaves a period in early endotoxaemia with a supposed scarcity of NO. The present study was conducted to examine the effects of external supplementation of NO on liver microcirculation and function. MATERIAL: 13 male Sprague Dawley rats. INTERVENTIONS: The rats underwent laparotomy, and the left liver lobe was exteriorised. All animals were given a bolus dose of endotoxin (LPS) 5 mg/kg intraportally. One group (n = 6) had a continuous infusion of sodium nitroprusside (SNP) 1.4 microg/kg per min started concurrently, the other group (n = 7) was treated with normal saline. The study was terminated after 3 h LPS. MEASUREMENTS AND RESULTS: Intravital microscopy was performed at baseline, at 2 h and 3 h LPS. Hepatic function was assessed by arterial ketone body ratio, acid base values, and bile flow. At baseline 1% of the sinusoids were without perfusion. After 2 h LPS this figure had risen to 9.8+/-1.5% in the SNP group versus 16.9+/-1.4% in the controls (p < 0.05 vs controls). The corresponding values after 3 h LPS were 13.5+/-1.5 versus 19.3+/-1.5% (p < 0.05 vs controls). The leukocyte count in sinusoids and venules had a similar development. Functional parameters were all slightly better preserved in the SNP group, but with no individual significance versus controls. CONCLUSIONS: Infusion of the NO donor SNP in early endotoxaemia attenuates the detrimental effects of LPS on liver microcirculation, most probably by alleviating a relative deficit of NO at the microcirculatory level.

Carolina rinse attenuates postischemic microvascular injury in rat small bowel isografts.

BACKGROUND: Apart from rejection-related events, the manifestation of ischemia/reperfusion (I/R) injury remains a major problem, hampering success in human small bowel transplantation (SBTx). Therefore the aim of this study was to determine the potential of Carolina rinse (CR) to attenuate microvascular reperfusion injury in rat intestinal isografts. METHODS: After 18 hours of cold preservation in 4 degrees C University of Wisconsin solution (UW), rat SBTx was performed. Immediately before reperfusion the intestine was flushed with 4 degrees C or 37 degrees C Ringer's lactate (RL, groups 1 and 2) or CR (groups 3 and 4), respectively. In vivo fluorescence microscopy was used to analyze the grafts' microcirculation. RESULTS: In group 1 severe microvascular I/R injury was observed in mucosa and muscle layers. Microcirculatory deterioration was paralleled by enhanced leukocyte accumulation in submucosal venules and by impaired subserosal lymphatic capillary drainage (FCLD). Rinsing the grafts with 37 degrees C RL attenuated leukocyte-endothelial cell interaction and improved subserosal FCLD; however, it did not affect mucosal microvascular reperfusion damage. In contrast, 4 degrees C CR dramatically improved nutritive perfusion within muscle and mucosa (p < 0.05) and attenuated leukocyte adherence within submucosal venules (p < 0.05). Additional prewarming of CR almost completely prevented mucosal I/R injury (p < 0.05 versus group 3) and caused a fourfold increase of FCLD. CONCLUSIONS. With this study we demonstrate that CR in combination with rewarming of the graft before reperfusion is an effective regimen to prevent leukocyte accumulation and to counteract microvascular injury after SBTx.

Eight hours' inhalation of prostacyclin (PGI2) in healthy lambs: effects on tracheal, bronchial, and alveolar morphology.

OBJECTIVE: To study potential toxic effects of long-term (8 h) inhaled prostacyclin (PGI2) on respiratory tract tissues. DESIGN: In a prospective, randomized order, either PGI2 (n =7) or normal saline (n = 7) was aerosolized during a time period of 8 h in healthy lambs. SETTING: Institute for Surgical Research of the Ludwig-Maximilians University of Munich. ANIMALS: 14 health, anesthetized, ventilated lambs. INTERVENTIONS: All animals were endotracheally intubated followed by tracheotomy. PGI2 solution or normal saline was administered with a jet nebulizer (delivery rate 4-10 ml/h; mass median diameter of aerosol particles 3.1 microns). MEASUREMENTS AND RESULTS: Histomorphological changes after 8-h inhalation of PGI2 solution were compared to those after 8-h inhalation of normal saline. Tracheal and bronchoalveolar tissues were examined by light and electron microscopy in order to assess tissue damage induced by inhaled PGI2. Pathological changes were ranked by a blinded observer following a graduation system ranging from "absence of pathological changes" to "maximal pathological changes". Abnormalities were restricted to the trachea (focal flattening of the epithelium, loss of cilia, slight inflammatory cell infiltration) and alveolar tissue (focal alveolar septal thickening with slight inflammatory cell infiltration), but no statistically significant differences between the PGI2 and control groups were encountered. CONCLUSION: Our findings indicate the absence of PGI2 aerosol-related respiratory tissue damage after 8-h inhalation of PGI2.

On the fine structure of arc-capillaries: true a.v. anastomoses or sphincter capillaries?

The arc-capillaries represent vessels of the terminal bed: they are not true arterio-venous anastomoses. They exhibit a typical capillary structure of their wall. The existence of smooth muscle cells and modified smooth muscle cells, such as epithelioid cells, cannot be demonstrated. Likewise, a specific activation by nerves does not exist. The arc-capillaries differ from the net-capillaries neither in the structure of their wall nor in diameter. At the origin of the arc-capillaries from the final arteriole there are no smooth muscle cells, only pericytes (adventitial cells). The arc-capillaries branch off where the final arteriole no longer possesses smooth muscle cells. The electron microscopic studies showed that arc-capillaries do not represent sphincter capillaries.

Evaluation of murine liver transmission electron micrographs by an innovative object-based quantitative image analysis system (Cellenger).

BACKGROUND: Transmission electron micrographs are widely used to demonstrate tissue damage. However, the results are qualitative and dependent on the experience of the investigator. Recently, a new multiscale object-based quantitative image analyzing systems (Cellenger) has been introduced to study highly textured black-and-white images. It is unknown, whether this system permits the quantitative image analysis of electron micrographs of parenchymal tissue. Therefore, we analyzed whether the Cellenge system permits the quantitative evaluation of electron micrographs of murine liver under normal conditions and after ischemia-reperfusion injury. The results were compared with those obtained by conventional qualitative classification. - METHOD: Transmission electron micrographs from murine liver that had been exposed to isolated reversible ischemia at hypothermic conditions of 4 degrees C, 15 degrees C, 26 degrees C and 37 degrees C, and of sham-operated animals, which served as controls (2 images per animal, n = 3 in each group), were analyzed qualitatively by an investigator with experience in electron microscopy. For quantitative analysis, the Cellenger was used and the following damage parameters were studied: ratio of area of endothelial cell nucleus to area of endothelial cell (N/C ratio), ratio of area of hepatocellular vacuoles to area of total hepatocyte cytoplasm (V/C ratio) and ratio of area of microvilli in the space of Disse to area of the sinusoids (M/S ratio). All values were sampled within one group (n=6) and the data given in [%] (MW +/- SEM). P-values were accepted as significant below 0.05. RESULTS: After normothermic ischemia, all quantitative damage parameter were significantly altered as compared to sham-operated animals (N/C 15 +/- 9% vs. 37 +/- 7%, V/C 18 +/- 4% vs. 0, and M/S 0 vs. 10 +/- 1%) and all hypothermia groups. The qualitative electron micrograph section analysis corresponded very well with these results. CONCLUSION: We demonstrate that an multiscale object-based quantitative analysis of transmission electron micrographs from mouse liver under control conditions and after I/R provide accurate classification of relevant tissue damage parameter. The system is now ready to use for further applications within the field of highly textured electron micrographs.

Optimizing the oxygen balance during initial reperfusion with 2,3-butanedione monoxime attenuates cardiac reperfusion injury.

The effect of 20 mmol/L butanedione monoxime on myocardial ischemia/reperfusion damage was studied in isolated guinea pig hearts. Three groups of hearts (n = 8) were perfused in the Langendorff mode and cardioplegic arrest was induced with St. Thomas Hospital II solution (STS) at 37 degrees C for 50 min. Myocardial oxygen demand, recovery of myocardial function, and creatine kinase release during 30 min of reperfusion were monitored. Preservation of myocardial ultrastructure was determined by electron microscopy. Control (C) hearts underwent cardioplegic arrest and reperfusion without treatment. BDM was added during cardioplegic arrest in BDMSTS hearts, or to the initial (20 min) reperfusate in BDMREP hearts. BDM during initial reperfusion markedly reduced O2 demand and prevented creatine kinase release from cardiac myocytes, resulting in improved recovery of myocardial function and attenuation of myocardial ultrastructural damage after washout of the drug. In contrast, addition of BDM to the cardioplegic solution provided no protection from ischemic or reperfusion injury.

Role of leukocyte plugging and edema in skeletal muscle ischemia-reperfusion injury.

The purpose of this study was to examine the relationship of increased capillary network resistance due to leukocyte-capillary plugging and tissue edema through macromolecular leakage to tissue injury after ischemia-reperfusion (I/R). After a 3-h complete ischemia in the dorsal skinfold chamber of the awake Syrian hamster, the following parameters were measured: vessel diameter, macromolecular leakage, erythrocyte velocity, adherent leukocytes, rolling leukocytes, freely flowing leukocytes, functional capillary density (FCD), propidium iodide (PI)-positive cell nuclei, and increase in network flow resistance due to leukocyte-capillary plugging. These measurements were made under baseline conditions and after 0.5 and 2 h of reperfusion for I/R alone, I/R with phalloidin (PL) treatment (to block leakage), and I/R with both PL and cytochalasin D (CD) (to block both leakage and plugging). Neither treatment had an effect on the leukocyte adherence or rolling. PL treatment preserved the endothelial barrier, improved FCD, and reduced the amount of PI measured tissue damage. CD treatment eliminated the increase in network resistance due to leukocyte plugging but did not improve FCD or tissue damage. Thus, in this I/R model, macromolecular leakage plays a role in tissue injury, whereas leukocyte plugging does not appear to be an important mechanism.